Method of treating paper with ethylenimine derivatives using a boron trifluoride-amine complex catalyst



United States Patent 3,428,484 METHOD OF TREATING PAPER WITH ETHYL- ENIMINE DERIVATIVES USING A BORON TRI- FLUORIDE-AMINE COMPLEX CATALYST Duane L. Kenaga, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Oct. 30, 1964, Ser. No. 407,894 The portion of the term of the patent subsequent to Apr. 4, 1984, has been disclaimed U.S. Cl. 117-155 13 Claims Int. Cl. D21h 3/36; C09d 3/48 ABSTRACT OF THE DISCLOSURE P aper treated with ethylenimine derivatives and a boron trifiuoride-amine complex in a substantially anhydrous system has improvement in one or more of the following characteristics: sizing, wet strength, dry strength, or flame-resistance.

This invention relates to an improved paper treating process. More particularly, the present invention relates to an improved method of treating paper with ethylenimine derivatives using a iboron trifluoride-amine complex as a curing agent.

It is known that tris(l-aziridinyl)phosphine oxide (APO) may be used in preparing fire retardant cell-ulosic fabrics as disclosed in US. Patent 3,034,919 to Steinhauer. Polyethylenimine has also been used for paper treatment. Other US. patents dealing With the use of APO in fiber treatment formulations include U.S. 2,859,- 134 to Reeves et al. and US. 2,870,042 to Chance et al. A particular method for treating paper with APO and certain derivatives is disclosed in US. Patent 3,312,520.

It has now been found that uniform curing of paper which has been impregnated with an ethylenimine derivative can he achieved by contacting the impregnated paper with a Iboron trifluoride-amine complex and then curing the impregnated paper. The most convenient method of contacting the impregnated paper with the curing agent is to add the curing agent to the ethylenimine derivative prior to impregnating the paper with the treating composition. The curing agents used in the process of the invention perform almost no curing function until heat is applied. When heat is applied to the boron trifluorideamine complex used in the process of the present invention, the complex decomposes and it is believed that the decomposition products (especially the BF that is liberated) effect a cure of the impregnated paper by reacting with the aziridine rings of the ethylenimine derivatives. Thus, :when the curing agents of the process of the present invention are used, both the rate and amount of cure can be precisely controlled to give a treated paper product of uniform quality.

As used herein, the term paper is meant to include cardboard, newspaper, brown utility paper and other foldable paper products derived from the kraft, sulfite, soda or other similar process.

The treatment process of this invention consistently results in improving one or more of the following characteristics of the treated paper: sizing (water repellency), wet strength, dry strength and/ or flame-resistance. In addition, other desirable properties such as folding endurance may show improvement when repeated runs are compared using the boron trifluoride-amine complexes according to the method herein disclosed,

The Fboron trifluoride-am'ine complex is a molecular complex (at least one amine-nitrogen atom per amine molecule is complexed with at least one molecule of BF and may be represented by the formula wherein A represents an amine (including polyamines) and n represents an integer of from one to the maximum number of amine-nitrogen atoms in the amine A. Examples of suitable BF -amine complexes include molecular complex compounds of the formula wherein each of R R and R is selected from group consisting of the hydrogen atom, a lower hydroxyalkyl group of the formula wherein k is an integer of from 2 to 4 and a lower alkyl group of from 1 to 4 carbon atoms and wherein at least one of R R and R is a lower alkyl group or a lower hydroxyalkyl group (i.e., not all of R R and R are hydrogen atoms). Typical curing agents in this class thus include:

H CHzCHzOH B F3-I I CH2 -CHQ, B Fa-N CH2CH20H C 3 B Fa-N-CH2CH2CH2OH, B Fa-F-CHaCH:

BFa-N etc.

Complexes in which the amine (A) is a heterocyclic amine -(such as piperidine, piperazine, morpholine, etc.) may also be used. Such complexes may be represented by the formula wherein x and y are each integers of from 1 to 3 and Z represents a methylene group, oxygen or an N-H group. When the amine moiety (A) is a heterocyclic tertiary amine, complexes such as formed with pyridine and pyrazine, respectively, may be used. The only requirement of the boron trifluorideamine complexes which are used as curing agents in the process of the invention is that the molecular complexes decompose at a temperature of from 50 to 250 C.

Complexes which decompose at temperatures of from 100 to 200 C. form a preferred subclass of curing algents. Other BF -ami11e complexes which may be used (boron trifiuoride-p,p'-methy1ene dianiline) and H2 C H B Fa-N-CHZOHZOHZNHR CH2CH3 (boron trifluorlde-diethylaminopropylamine) The ethylenimine derivatives which may be employed in the process of the invention are activated aziridine compounds which contain at least one substituted or unsubstituted aziridine ring of the formula wherein R is hydrogen or a hydrocarbon of from 1 to 6 carbon atoms such as an aryl group, alkyl group, alkenyl, cycloalkyl or cycloal-kenyl group. Since the physical and chemical modifications of the paper are achieved by the opening of the aziridine (or substituted aziridine) rings coupled with the combination of these opened rings with the cellulose molecules of the paper, any compound with an activated aziridine ring which may be cleaved by the BF -amine complex may be used in the process. The properties of the paper will vary with the particular ethylenimine derivative employed and will depend somewhat upon the other elements and structural groups within the molecule. Thus, when phosphorus or halogen atoms are present in the ethylenimine derivative compound, the cured paper product will have fire-resistant properties.

By activated aziridine compound as used herein is meant an aziridine compound which contains substituents attached directly to the aziridine nitrogen atom which are capable of stabilizing a negative charge which is formed on the aziridine nitrogen in the transition state when the compound reacts with a nucleophile. A particular class of such compounds include those which are characterized by the structure (which may be monovalent or divalent) wherein R is as previously defined, M is a phosphorus or carbon atom and X represents a sulfur atom or an oxygen atom. Typical examples include l-acetyl aziridine, ethyl aziridinyl formate and O-cyclohexyl-N,N-ethyleneurethane.

Since one of the main advantages of the process of the invention is to provide a means for COIltI'Ollll'lig the curing step in order to obtain 'uniform results, it is desirable to eliminate other materials from the treating composition which might cause premature or partial curing of the composition by uncontrolled cleavage of the aziridine ring. Thus, it is preferable to use an inert solvent in preparing a treating bath. Since substances such as acids tend to open the aziridine ring, it is preferable that such substances be omitted from the treating composition. However, small amounts of acid or other ringopening materials may nevertheless be present in the treating bath. Optimum results are obtained when these other conventional aziridine ring-opening reagents and/ or polymerization catalysts are eliminated from the treating compositions. Examples of solvents which may be used include xylene, toluene, benzene, 1,1,l-trichloroethane, carbon tetrachloride, chloroform, ethylene dichloride, ethylene dibromide, perchloroethylene, trichloroethylene, chlorobenzenes, aliphatic naphthas, gasoline, aromatic mineral spirals, n-butane, n-pentane, isopentane, ethylbenzene and mixtures of such solvents.

In a preferred embodiment of the invention, a bath mixture is prepared containing from .2 to 10 percent by weight of an activated ethylenimine derivative and a catalytic amount (usually from .1 to 20.0 percent by weight based on the amount of aziridine compound) of boron trifiuoride-atmine complex dispersed or dissolved in a suitable inert (preferably substantially anhydrous) solvent or carrier. The paper which is to be treated is contacted with the bath by any suitable method (dipping, spraying, brushing, etc.) to form a product impregnated with the desired amount of activated ethylenimine derivative and catalyst. The impregnated paper product may be dried prior to curing or may be simultaneously dried and cured by the application of heat to the treated paper. The heat curing step may be carried out at temperatures of 'from about 50 to 250 C. Temperatures of from to C. are generally sufficient to cure most treated paper products in a time period of about four minutes.

The preferred activated ethylenimine derivatives which are used in the process are phosphine oxides or sulfides of the formula (each R is as previously defined), a phenyl group and an alkoxy group of from 1 to 18 carbon atoms. Examples of such compounds include Other suitable compounds which may be used in the process of the invention are discolsed in US. Patents 2,606,901 and 2,606,902 to Parker et al., the disclosures of which are herein incorporated by reference.

The following examples are submitted for the purpose of illustration only and are not to be construed as limiting the scope of the invention in any way.

Example I Preformed handsheet [dimensions 9" x 11"; TAPPI (Technical Association of the Pulp and Paper Industry) basis weight-70.3 grams/sq. meter] of Weyerhaeuser Regular (bleached) Kraft were dipped in treating baths containing 2.0 percent and 4.0 percent of tris(1-aziridinyl)phosphine oxide (APO) and an amount of BF amine complex equal to 9.0 percent BF by weight based on the APO in the treating bath. The solvent was allowed to evaporate at room temperature and the impregnated sheet was placed between two cauls on top of a felt pad and cured in a laboratory press at temperatures of 90 C. or 120 C. (top platen temperature) for a time period of four minutes. The .solvent used to prepare the bath was a mixture of 1,1,1-trichloroethane and methyl ethyl ketone (75:25 parts by volume, respectively). The catalyst BF -DEAPA (diethylaminopropylamine) of Runs 5 and 6 was not soluble in this carrier. All catalysts of Runs l12 were therefore dissolved in dimethyl forma-rnide and then mixed with the bath (containing 1,1,1,- trichloroethane, methyl ethyl ketone and APO). The results are summarized in Table 1.

The following tests were employed:

(1) Bursting strength.The bursting strength of paper is defined as the hydrostatic pressure (in pounds per square inch) required to rupture the material when pressure is applied at a controlled increasing rate through a rubber diaphragm to a circular area of material 1.20 inches in diameter. The test is designated as TAPPI Standard T403 rn-53. Both wet and dry burst strength are measured. Wet strength is determined using a paper specimen which has been soaked in deionized water for 24 hours at room temperature. Burst factors are calculated to correct for the basis weight of each sheet to the standard TAPPI ream of 70.3 grams per square meter.

(2) Sizing.-This test measures the time (in seconds) required to establish a flow of a given quantity of electricity through a paper specimen placed between a lower, zinc electrode and an upper porous, water-soaked, bronze electrode.

(3) Tensile breaking length-This is the calculated length (in meters) required for a strip of paper to break 6 under its own weight. TAPPI Standard T404 os-61 (for /2 inch width).

Definition of terms used in Tables 1-5:

Burst factors (1) Burst Factor (Dry Burst Factor:DBF, Wet Burst F actor:WBF)

70.3XBur-st Test Actual Basis Weight in g./rn.

(2) Percent Dry Increase:

DBFDBF of Control DBF of Control X (3) Wet/Dry Control Percent:

WBF X 100 (4) Percent Wet/Dry:

WBF x100 35716 Tensile Test (0.5 strip) Actual Basis Weight in g./m.

(6) Percent Dry Increase:

DBLDBL of Control DBL of Control (7) Wet/Dry Control Percent:

WBL DBL of Control (8) Percent Wet/Dry Length:

In this application, the symbol is meant to represent an unsubstituted aziridinyl group TABLE 1 Percent Burst Strength Tensile Breaking Length Run APO Catalyst F in Percent APO Temp. No. Treating Used Treating Retained by of Cure, Percent Wet/Dry Percent Wet/Dry Concentration Solution Analysis 1 C. D Control, Dry Control,

Increase Percent Increase Percent 2.0 BF;-MEA .18 1.76 90 7.8 4.0 BF M EA. 36 2. 37 90 10.1 16.1 2.0 BF -MDA 18 1. 23 90 13. 2 16. 0 4. 0 BF -MD 36 2. 68 90 36. 9 35. 3 2. 0 BF -DEAPA- 18 1. 13 90 6. 6 8. 5 4. 0 BF -DEAPA- 36 2. 97 90 8. 1 17. 0 2.0 BF -MEA-- 18 1. 46 10. 0 13.0 4. 0 BF -MEA 36 2.07 120 14. 8 19. I 2.0 BF -MD l8 1. 61 120 20. 6 20.3 4.0 BF -MDA 36 2. 91 120 45.0 36.0 2.0 BFa-DEAPA- 18 1. 77 120 7. 1 9. 3 4. 0 BF -D EAPA- 36 3. 89 120 12.6 16. 2

1 Percent APO retained was calculated on the basis of nitrogen ratio present in the treating solution. Percenta e is by welglat based upon the dry weight of the paper. Figures in parentheses are actual values for the controls. (Dry burst factors and breaking length in meters.

EH H

7 Example II Preformed handsheets of Weyerhaeuser regular bleached kraft pulp (approximately 400 milliliters Canadian Standard Freeness) were treated by dipping in solvents containing APO and catalysts. The BF -amine catalysts were prepared in methyl alcohol as stock solutions and the APO was prepared in 1,1,1-trichloroethane as a 16 percent by weight stock solution. Treating baths were prepared on the basis of the final density of the mixture of 1,1,1-trichloroethane and methyl alcohol, proper dilution being made to give a 15 percent by weight concentration of BF -amine complex based upon the total weight of APO in the treating bath.

Cure temperatures and times were varied in a series of experiments. The temperature of each sheet was fol- 8 Example III Handsheets of Abitibi spruce kraft were treated with a bath of 1,1,1-trichloroethane and methyl ethyl ketone (volume ratio of 3:1, respectively) containing APO and BF -amine complexes in varying concentration ranges.

CHzCHz gives results comparable to BF -alkylamine complexes lowed by means of a fine wire thermocouple and recording instrument. The curing step was carried out by placing the impregnated sheet (after evaporation of the solvent) on a highly polished caul. The other surface was against a blotter and felt pad. This assembly, felt side down, was placed on a cold lower platen of a press and then raised against the hot upper platen. The thermocouple was inserted between the caul and the sheet. The results are recorded in Tables 2 and 3.

TABLE 2 Preformed handsheets of Weyerhaeuser (bleached) kraft and Weyerhaeuser unbleached Douglas fir kraft were treated with baths containing APO. Incorporated into the bath liquids (a 3:1 volume mixture of 1,1,1-trichloroethane and methyl ethyl ketone, respectively) in addition to APO were BF -N(CH CH O-H) (BF -TEA) and BF -hexamethylenetetramine (BF -HMT) complexes. The results are summarized in Table 5. In each lBF -Monoethylamine as Catalyst [Percent Weight Concentration in Treating Bath=15 Percent on Concentration 01' APO in Treating Bath] (i.e., for Every Gram of APO There is .15 Gram of BFr-Monoethylaminefl APO Cure Conditions Burst Strength Tensile Breaking Length Run No In Soln., On Sheet Tern Time Wet/Dry Percent Wet/Dry Percent Percent by Analysis, of (Mins.) Control, Wet/Dry Control, Wet/Dry Percent Percent Percent TABLE 3 [BF;-p,p-Methylenedianiline as Catalyst [Percent Concentration in Treating Bath=1o.18 Percent on Percent Concentration of APO in Treating Bath] (i.e., for Every Gram of APO There is .1018 Gram of BFa-p,p-Methylenedianiline)] APO Cure Conditions Burst Strength Tensile Breaking Length Run No. In Soln., On Sheet Temp. Time Wet/Dry Percent Control, Percent Percent by Analysis, 0.) (Mins.) Control, Wet/Dry Wet Dry Wet Dry Percent Percent Percent run in Table 5, the concentration of the tris(1-aziridin l) phosphme oxide (APO) 1n the treating bath was 4.0 percent based on the total weight of the treating bath.

TABLE 5 Burst Tensile Curing Percent (Wt. Stren th Break L Run No. Type of Paper Catalyst Temp. of Catalyst in g mg ength C.) Treating Beth Percent Percent Wet/Dry Wet/Dry Control Control BF3-TEA 120 1. 15 61. 7 44. 1 -HM 120 o. 73 e4. 0 44.3 2 -TEA 120 1. 15 61. 5 45.0 .d -HM 120 0.73 55. 3 41, e 3 BF -TEA. 1. 15 65. 0 51. 4 d0- BFB'HM 150 0. 73 68,1 50, 4 {Unbleached Douglas fir krait. BF -TE 150 1. 15 67. 5 56, 5 ..-d Fa-HMT 150 0.73 57. 2 50, 7

10 impregnated paper samples were cured at temperatures of 120 C. and 190 C. for a 4 minute time period. The simi properties of the treated and untreated paper were compared. The results are summarized in Table 6.

In this work the percent dry burst is defined as the difference in the burst in p.s.i. of the treated specimen and the control specimen divided by the burst in p.s.i. of the control specimenx 100. No correction has been made for "basis weight.

The wet burst is the actual burst in p.s.i. recorded after 24 hours soak in deionized water. The untreated control specimens have essentially 0 p.s.i. burst strength.

TABLE 6 Percent Dry Burst Wet Burst Sizing Without With Without With Without With Catalyst BF3.MEA Catalyst BFfl-MEA Catalyst BF -MEA Catalyst Catalyst Catalyst Example V Compound R=CHa R=CH;

The following runs were carried out in a manner n u u u n a u n as M M m M m m M M ww n n u u h u n 2 u n n n u u n u 26 m m m m m m m m m m at n u n u a n n u n s n n u u u u u n n RR 5 6 3 nm 0 2 Z6. 2 & 4 d 1 n u 11 1 69 26 mom h L7. 0 9% L4 L6. t I 2. 4 I 2 I 7.. an. m m m no mm m m an m m m 90 M W 65 37 87 W w 31 m W an. m m as 4.0.. at. m m m m n m I I N 0 0 m n N H one w O" C H J m 0 4. a H N C 0 a in H I m m C 4 a C w w w wk? 4 Eva w w M H N R R R R R R I. R R R R R 2" 3 4" 5 lar to that shown in the preceding examples. Chromatography paper (Whatman No. l) was cut into sheets 4 /2 by 6 /2 inches and dipped in a 35 milliliter treating bath containing 2 percent by weight of an aziridine derivative test compound. The liquid portion of the bath was a :50 (volume) mixture of xylene and methyl ethyl ketone. Some of the treating baths also contained .30 percent (weight) of BF -CH CH NH catalyst to compare the effect with catalyst and without catalyst. The dried Run Number R-NH-C- Table 6-Uontinued Percent Dry Burst Wet Burst Sizing Run Number Compound Without With Without With Without With Catalyst BFa.MEA Catalyst BFnMEA Catalyst BFa.MEA

Catalyst Catalyst Catalyst -0 27.4 3.0 9.5 R=CH:,N- 27. 4. 43. 7 11. 2 13. 1

O W H 6 RI.N

H OH:

7 l r-a 50 Percent mixture 01- (R=o3H1o 1-2 3 0 and R=C3H1s 6. 0 7- 9 CHaH S II 1.1 138.4 9 011 27 0 0 J u 22 110.0

In the foregoing examples, it is to be understood that all unsatisfied valences of the carbon atoms are bonded to hydrogen atoms.

We claim as our invention:

1. A method of paper treatment which comprises contacting paper with a substantially anhydrous mixture containing a BF -amine complex and a compound having the formula wherein:

(a) X represents an atom of atomic number 8k where k is an integer of from 1 to 2,

(b) each R is independently selected from the group consisting of the phenyl group and a group of the formula tc Hzm-lH in which in is an integer of from 0 to 4, and

(c) each Y is independently selected from the group consising of (wherein each R is as previously defined) and an alkoxy group of from 1 to 18 carbon atoms and curing said impregnated paper at a temperature of from about 50 C. to 250 C.

2. The method of claim 1 wherein the BF -amine complex has the formula 3. The method of claim 1 wherein the BF -amine complex is:

CHzCHz CHzC 2 B Fa-NN 4. The method of claim 1 wherein the BFyamine complex is:

5. The method of claim 1 wherein the BF -amine complex is BF CH CH NH 6. The method of claim 1 wherein the mixture contains tris (l-aziridinyl) phosphine oxide and a BF -amine complex as the only curing catalyst to form an impregnated paper product, and the curing is at a temperature of from about to 200 C.

7. The method of claim 1 wherein the mixture contains tridecyloxy bis(1-aziridinyl)phosphine oxide and a 13 14 BF 'amine complex to form an impregnated paper pro- 13. The method of claim 7 wherein the BF -amine duct and the curing is at a temperature of from about complex is BF -hexamethylenetetramine. 100 to 200 C.

8. The method of claim 1 'WhCI61I1 the mixture contains ferences C ted 5 UNITED STATES PATENTS j O H 9f 2,859,134 11/1958 Reeves et a1. 117-441 X I; OH I I N 2,870,042 1/1959 Chance et a1. 117-136 N- 2,886,539 5/1959 Drake etal. H2 H2 2,891,877 6/ 1959 Chance et al. 10 2,901,444 8/1959 Chance et al. and a catalytlc amount of 2,917,492 12/1959 Reeves et a1 117-136 X 3,034,919 5/1962 Steinhauer 117-121 X 3,242,004 3/1966 Kenaga 117-136 BFa-IIF-CHZCIIS 15 3,312,520 4/1967 Kenaga 117-6O X H OTHER REFERENCES to form an impregnated Paper product Drake, George L, Jr.: Imparting Crease Resistance The method f claim 6 wherein the BF3.amine and Crease Retention to Cotton With APO, Textile Recomplexis BFs.hexamethy1enetetmmine search Journal, vol. XXIX, No. 2, February 1959.

1 6 h th BF in 3 3,: W mm 6 3 am 6 WILLIAM D. MARTIN, Primary Examiner.

11.-The method of claim 7 wherein the BF -amine M LU$1GNAN, Aysistant E i complex is BF -H N-CH CH 12. The method of claim 7 wherein the BF -amine U.S.Cl.X.R. complex is BF -N(CH CH OH) 117137, 161; 2602 

